jade.content.onto
Class Ontology

java.lang.Object
  |
  +--jade.content.onto.Ontology

Direct Known Subclasses:

FullOntology

public abstract class Ontology

extends java.lang.Object

An application-specific ontology describes the elements that agents can use within content of messages. It defines a vocabulary and relationships between the elements in such a vocabulary. The relationships can be:

• structural, e.g., the predicate fatherOf accepts two parameters, a father and a set of children;
• semantic, e.g., a concept of class Man is also of class Person.

Application-specific ontologies are implemented through objects of class Ontology.
An ontology is characterized by:

• one name;
• one base ontology that it extends;
• a set of element schemata.

Element schemata are objects describing the structure of concepts, actions, predicate, etc. that are allowed in messages. For example, People ontology contains an element schema called Person. This schema states that a Person is characterized by a name and by an address: ConceptSchema personSchema = new ConceptSchema(PERSON); personSchema.addSlot(NAME, stringSchema); personSchema.addSlot(ADDRESS, addressSchema, ObjectSchema.OPTIONAL); where PERSON, NAME and ADDRESS are string constants. When you register your schema with the ontology, such constants become part of the vocabulary of the ontology.
Schemata that describe concepts support inheritance (this is not true for all other schemata, e.g., predicates, actions, etc.). You can define the concept Man as a refinement of the concept Person: ConceptSchema manSchema = new ConceptSchema(MAN); manSchema.addSuperClass(personSchema); Each element schema can be associated with a Java class to map elements of the ontology that comply with a schema with Java objects of that class. The following is a class that might be associated with the Person schema: public class Person extends Concept { private String name = null; private Address address = null; public void setName(String name) { this.name = name; } public void setAddress(Address address) { this.address = address; } public String getName() { return name; } public Address getAddress() { return address; } } When sending/receiving messages you can represent your content in terms of objects belonging to classes that the ontology associates with schemata.
As the previous example suggests, you cannot use objects of class Person when asking for the value of some attribute, e.g., when asking for the value of address. Basically, the problem is that you cannot 'assign' a variable to an attribute of an object, i.e., you cannot write something like: person.setName(new Variable("X")).
In order to solve this problem, you can describe your content in terms of abstract descriptors. An abstract descriptor is an object that reifies an element of the ontology. The following is the definition of the abstract descriptor for the concept Person: AbsConcept absPerson = new AbsConcept(MAN); absPerson.setSlot(NAME, "John"); absPerson.setSlot(ADDRESS, absAddress); where absAddress is the abstract descriptor for the Mary's address: AbsConcept absAddress = new AbsConcept(ADDRESS); absAddress.setSlot(CITY, "London"); Objects of class Ontology allows you to:

• register schemata with associated (i) a mandatory terms of the vocabulary and, e.g., NAME (ii) an optional Java class, e.g., Person;
• retrieve the registered information through various keys.

The framework provides two ontologies that you can use for building your application-specific ontologies:

• BasicOntology: that provides all basic elements, i.e., primitive data types, aggregate types, etc.
• ACLOntology: that extends the BasicOntology to provide the elements that the semantics of the FIPA ACL mandates, e.g., the Done modality, variables with an associated cardinality, etc.

Application-specific ontologies should be implemented extending the ACLOntology.

Author:

Federico Bergenti - Universita` di Parma

See Also:

Concept, jade.content.abs.Concept, ACLOntology, BasicOntology, ConceptSchema

Field Summary

protected Ontology	base
protected java.lang.String	name

Constructor Summary

Ontology(java.lang.String name)
Construct an ontology with a given name

Ontology(java.lang.String name, Ontology base)
Construct an ontology with a given name that extends base.

Method Summary

abstract void	add(ObjectSchema schema) Adds a schema to the ontology
abstract void	add(ObjectSchema schema, java.lang.Class javaClass) Adds a schema to the ontology and associates it to the class javaClass
abstract AbsObject	fromObject(java.lang.Object obj) Converts an object to an abstract descriptor.
abstract java.lang.Class	getClass(java.lang.String name) Retrieves the concrete class associated with name in the vocabulary.
java.lang.String	getName() Retrieves the name of the ontology.
abstract ObjectSchema	getSchema(java.lang.Class javaClass) Retrieves the schema associated with javaClass
abstract ObjectSchema	getSchema(java.lang.String name) Retrieves the schema associated with name.
abstract java.lang.Object	toObject(AbsObject abs) Converts an abstract descriptor to an object.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

base

protected Ontology base

name

protected java.lang.String name

Constructor Detail

Ontology

public Ontology(java.lang.String name)

Construct an ontology with a given name

Parameters:

name - identifier of the ontology.

Ontology

public Ontology(java.lang.String name,
                Ontology base)

Construct an ontology with a given name that extends base.

Parameters:

name - identifier of the ontology.

base - base ontology.

Method Detail

getName

public java.lang.String getName()

Retrieves the name of the ontology.

Returns:

the name of the ontology.

add

public abstract void add(ObjectSchema schema)
                  throws OntologyException

Adds a schema to the ontology

Parameters:

schema - the schema to add

Throws:

OntologyException -

add

public abstract void add(ObjectSchema schema,
                         java.lang.Class javaClass)
                  throws OntologyException

Adds a schema to the ontology and associates it to the class javaClass

Parameters:

schema - the schema.

javaClass - the concrete class.

Throws:

OntologyException -

getSchema

public abstract ObjectSchema getSchema(java.lang.String name)
                                throws OntologyException

Retrieves the schema associated with name.

Parameters:

name - the name of the schema in the vocabulary.

Returns:

the schema.

Throws:

OntologyException -

getSchema

public abstract ObjectSchema getSchema(java.lang.Class javaClass)
                                throws OntologyException

Retrieves the schema associated with javaClass

Parameters:

javaClass - the Java class

Returns:

the schema

Throws:

OntologyException -

getClass

public abstract java.lang.Class getClass(java.lang.String name)
                                  throws OntologyException

Retrieves the concrete class associated with name in the vocabulary.

Parameters:

name - the name of the schema.

Returns:

the Java class.

Throws:

OntologyException -

toObject

public abstract java.lang.Object toObject(AbsObject abs)
                                   throws OntologyException,
                                          UngroundedException

Converts an abstract descriptor to an object.

Parameters:

abs - the abstract descriptor.

Returns:

the object

Throws:

OntologyException -

UngroundedException -

See Also:

fromObject(Object)

fromObject

public abstract AbsObject fromObject(java.lang.Object obj)
                              throws OntologyException

Converts an object to an abstract descriptor.

Parameters:

obj - the object

Returns:

the abstract descriptor.

Throws:

OntologyException -

See Also:

toObject(AbsObject)